The use of blow-molding as a method for manufacturing various sorts of articles is generally well known. Typically, this process involves the use of a mold consisting of two separate halves or portions having cavities of particularly desired shapes and sizes. Usually, one extrudes a large-diameter, sealed tube of molten material (commonly referred to as a “parison”), places the tube between the mold halves, and closes the mold around the tube. Fluid pressure is then introduced into the tube, forcing the molten tube against the walls of the cavities, conforming the tube to the shape thereof. The pressure is maintained until the molten material cools and solidifies. The pressure is then released, the mold halves are pulled apart, and the hardened article is ejected therefrom.
Many types of articles are manufactured in this manner in order to produce a double wall body. By producing an article in this manner, one is able to easily create an article that has two, hard plastic walls with a buffering space between them, thereby resulting in a body with a multitude of desirable physical characteristics, such as strength, rigidity, scuff resistance, and impact absorption, but that is also relatively inexpensive to manufacture. Because blow molding is a fairly simple way of producing a double wall article which is both inexpensive and lightweight, yet also strong and durable, it is not uncommon to use this method for manufacturing various types of housings and cases for machinery, tools, and industrial applications.
When manufacturing double wall articles of this nature, the mold in which the parison is placed often includes a first half, which has a recessed surface that serves as part of the mold cavity surface against which the wall of the blow molded article is blown, and a “core” half, which generally contains at least one projecting (or “male”) section, over which the molten parison drapes as the mold is closed. When fluid pressure is subsequently introduced into the parison, molten material is pressed against the projecting mold section, conforming the tube to the shape thereof, where it cools, shrinks, and solidifies. An example of such a system is disclosed in U.S. Pat. No. 6,348,173, which is assigned to the assignee of the present application. Accordingly, with this type of mold, the projecting section of the mold core can be used to cause a large portion of the article to a thin, double wall structure, while the remainder to the article—such as the perimeter surrounding the thin portion, may comprises a thicker double wall structure.
One way in which these types of articles can be improved, however, is by utilizing the ability to create space between the walls to produce articles that can hold items, such as machine manuals or accessories. It is known that one way of doing this is to create a double wall article using two mold halves that have recessed mold surfaces that are fairly well spaced apart when the mold is in a closed position, such that a wide cavity is created therebetween, where the surface of a punch comprises part of one of the mold surfaces. The punch, when in an unactivated position, forms a portion of mold surface, against which the walls of the blow molded case are blown. Then, at a predetermined interval, before the walls of the case are fully hardened, the punch is moved to an activated position, creating a hole in the wall of the case.
Examples of such a system are disclosed in U.S. patent application Ser. Nos. 10/958,824 and 11/105,721, each of which is assigned to the assignee of the present application, which deal with the formation of double wall, blow molded cases. During the blow molding process, the parison is blown against these mold surfaces (one of which includes a portion of the punch) to form the walls of the blow molded article. Early in the molding cycle, while the walls of the article are still somewhat molten, the punch is activated, at which time the punch's cutting surface cuts through the wall and enters the mold cavity. The punch is then withdrawn, and subsequently, the mold is opened and the blow molded article removed.
In these systems, the punch generally moves in the direction in which the mold portions are moved when the mold is closed. This allows the punching forces to be backed by the press portion of the mold and allows for relatively uncomplicated part removal, and allows for minor angles and steps incorporated in the punch cylinders. Accordingly, the resultant holes are parallel to the parting line and serve to remove a portion of one the walls that forms the rigid, double wall structure. While these devices are very advantageous in applications such as cases and other types of closeable containers, they may not be practical in other applications.
This is especially true, for example, in applications where it is not desired that another, corresponding part, such as a lid, be required to cover the hole. Unlike in the instance of portable cases—which include a cover to retain the items being carried in the case when carried in a vertical orientation, and which can be lain horizontally when the case is opened to access the items—in other applications, it may be desired to mount a receptacle in a vertical position. In these situations, a hole in one of the larger surfaces of the receptacle would be virtually useless, as any items place therein would fall out as soon as they weren't restrained. In these types of applications, the area that is made available by creating a hole in a wall of the article should be able to retain the items independently of any restraining device.
This type of arrangement may be desired in a wide variety of situations. For example, it may be desired to vertically orient a receptacle by mounting it to a machine or a vehicle, such as, for example, a tractor or forklift, in order to house documents or books that may need to be accessed by the user, such as instruction/operation manuals, maintenance records, or floor layouts. Alternatively, it may be desired to mount such a receptacle to certain machinery in order to hold other types of items, such as, for example, to an aerial lift in order to house safety harness equipment. Additionally, there may also be applications in which it is desirable to retain the integrity of the double wall structure along substantially the entire length of the receptacle.
What is desired, therefore, is a blow molded, double wall receptacle with an opening to the cavity between the walls that is somewhat horizontal when the receptacle is oriented in a vertical position, as well as a system for punching such a hole. What is also desired is a blow molded, double wall receptacle that essentially retains a double wall structure along its length.
Additionally, punching a hole in a somewhat horizontal wall as described above presents several challenges. For example, shrinkage of the hardened plastic onto the sidewalls of a mold core can sometimes restrict the punching action and prohibit part removal. Additionally, the force supplied by the punch cylinder will sometimes be insufficient to cut through the wall, for several reasons. First, because the process involves a sidewall, and thus, the punching action must occur substantially perpendicular to the open-close direction of the mold, the cylinder will not be supported by the press portion of the mold, and therefore, the cylinder will have to be even larger to supply the necessary power and speed. At the same time, if the cylinder is located in the mold core, the size of the cylinder is necessarily limited due to space constraints. Similarly, the positioning of the punch controlled by a cylinder in-line with the punch is limited due to the diameter of the cylinder, and thus, the punch could not be located at the top of the mold core in order accommodate for the width of the cylinder.
What is further desired, therefore, is a system for creating a blow molded, double wall receptacle of the aforementioned type that does not limit the size of the punch cylinder. What is also desired is a system for creating a blow molded, double wall receptacle of the aforementioned type that does not limit the positioning of the punch.